1. Field of the Invention
This disclosure relates to acrylamide-based crosslinking monomers and methacrylamide-based crosslinking monomers. More particularly, this disclosure relates to processes for preparing acrylamide-based crosslinking monomers and methacrylamide-based crosslinking monomers, and to their uses for preparing adhesives, membranes, coatings, and ion exchange resin.
2. Description of Related Art
Free-radical crosslinking polymerizations and copolymerizations of crosslinking monomers with two or more ethylenic groups have been used for preparation of coatings, adhesives, membrane formations and resin preparations. These crosslinking monomers are generally multifunctional acrylate monomers and methacrylate monomers exemplified by hexanediol diacrylate, or alternatively, are acrylated oligomers exemplified by acrylated urethanes, epoxies, polyesters and acrylics. They are commercially available from coating chemical suppliers exemplified by Sartomer USA LLC (Exton, Pa., USA) and Cytec Industries Inc. (Woodland Park, N.J., USA). A disadvantage of these acrylic/methacrylic ester crosslinking monomers is that they degrade rapidly in the presence of caustic substance such as sodium hydroxide solution or in the presence of acid substance such as hydrochloric acid.
In contrast, acrylamide-based crosslinking monomers are much stable under caustic/acidic conditions. N,N′-methylenebisacrylamide only shows slight degradation at pH 14. Methylenebisacrylamide is a crystalline compound and its crosslinking network is very brittle. In addition, methylenebisacrylamide has low solubility (less than 10 wt %) in general solvents such as ethanol, water, and N-methyl pyrrolidone and thus has limited uses in coatings and resins where relatively high crosslinking density is required. Typical processes for preparation of acrylamide-based monomers generally comprise reacting an amine compound with one of an anhydride and an acid chloride. Such processes use expensive and hazardous acid chlorides or anhydride and generate byproducts that are difficult and expensive to remove. There are no other acrylamide-based crosslinking monomers commercially available.